#include <iostream>
#include <algorithm>
using namespace std;
bool isPrime(int n) {
    if (n < 2) return false;
    for (int i = 2; i * i <= n; ++i) {
        if (n % i == 0) return false;
        }
        return true;
        }
        int main() { 
            int n;
            cin >> n;
            if (n < 1000 || n > 9999) {
                cout << 0 << endl;
                return 0;
                }
                string s = to_string(n);
                sort(s.begin(), s.end());
                int ans = 0;
                do {
                int num = stoi(s);
                if (isPrime(num) && num > ans) {
                    ans = num;
                    }
                    } while (next_permutation(s.begin(), s.end()));
                    cout << ans << endl;
                    return 0; 
            
        }
